Yes you can get pretty much cash from selling scrolls. The last obelisks are in undead land. I dont know where in the game you are but if you reach undeads u can have them all

Yes, sell them, preferably with the level 3 Trade skill.

All the obelisk locations are listed on the gamebanshee.com site, where they have lots of useful info on the game.

2. Major Jumps in Difficulty in Main Quest
I think this one might be partially as a result of my first concern, but it's the main reason I'm stuck in The Legend. Every time I finally start to make progress in the story, they send me to a new area where everything is suddenly "Overpowering" or "Impossible" and I'm left wondering what I need to do to catch up. I'm definitely going to play Armored Princess on easy if I get it, that's for sure.

The first four Islands in AP are easy, but most people who have played it note that there is a vast jump in enemy army difficulties from the fifth Island on with;)

There is no main quest in ap at all :p you can do whatever order. For begginer it might be hard indeed but if you got familair with game it wont. Personally i played on imposssible difficutly and i decided that after rusty i did not go to Verona, would be too easy. I went to Nameless ^^ 3 times harder than Verona xD.Enemies armies wiere 15-20 times larger than mine but stil i could win :>
With just one unit, not 5. And cleraed all. Even few fights without any unit lost :P